Alloy metals for use in dental castings



Patented Nov. 11, 1952 UNITED STATES PATENT OFFICE ALLOY METALS FOR USE IN DENTAL CASTINGS Hugh P. Owens, Detroit, and Emil Grady, Wayne, Mich.

3 Claims.

The invention concerns an alloy suitable for dental castings and also concerns a method of preparing the alloy. The invention also relates to a method of successfully incorporating titanium with other metals for use in dental castmgs.

The selection of metals and alloys for use in dental castings has been sharply limited because of the requirement that the metal or alloy must be capable of being readily cast and that the piece as cast must possess considerable strength without heat treatment. In the development of this art particular stress has been placed on the strength of the casting and a strong, but substantially rigid, casting has been developed. The high tensile strength is necessary in order that the clasps of a partial plate remain firmly in place on the anchor teeth and, in this connection, the necessity for securing a tight fit has in the past resulted in the application of a significant pressure of the clasp against the anchor teeth which in turn causes the latter to be pulled out of alignment after several years of use.

It is, therefore, one of the principal objects of:

this invention to provide an alloy which has a high tensile strength as cast; which possesses sufiicient spring to enable the clasp of a partial dental plate to be expanded considerably for easy positioning on the anchor teeth; which, following such expansion, will return to its original setting; and which has give such that the anchor teeth will not be pulled out of alignment even during many years of use.

In the forming of the alloy of the invention and in the forming of alloys for other uses, it is frequently desirable to incorporate relatively large percentages of titanium. The latter, however, has the unfortunate property, when added to a molten bath, of reacting with oxygen and nitrogen to form oxides and nitrides of titanium. It is, therefore, a principal object of this invention to provide a method for the successful incorporation of relatively large percentages of titanium into alloys.

I have found that the foregoing and related objects can be secured with an alloy comprising essentially the following ingredients in approximately the percentage range indicated:

Carbon Manganese -1.00-2.00 Silicon LOO-2.00 Chromium 20.00-30.00 Cobalt 14.00-35.00 Nickel 5.00-12.00 Zirconium 1.00-5.00 Titanium 0.15-10.00 Tungsten (or molybdenum) 2.50-3.00 Iron Balance.

A11 percentage figures given in this specification and the appended claims are percents by weight.

The method of the invention comprises the melting of the metal or alloy to which titanium is to be added; then adding a small percentage; preferably more than about 0.5%, of zirconium, and then immediately adding the titanium.

Although the invention broadly encompasses the metals in the proportions outlined above; we have found that best results are secured using alloys with somewhat more restricted proportions of certain of the constituent metals. Particularly, we have found that the percentage of nickel should be relatively higher when the percentages of chromium, cobalt, and titanium are relatively low. The following represent the two alloys which are superior:

Carbon 0.25-0.50 Manganese. LOO-2.00 Silicon 1-- LOO-2.00

, Chromium 20.00-25.00

Gobalt l-.. 14.00-20.00

Nickel 10.00-12.00 Zirconium 1.00-5.00 Titanium wi h 0.15-2.00 Tungsten 2.50-3.00 Iron Balance.

Carbon' 0.50-0.75 v Manganese LOO-2.00 Silicon 1.00-2.00 Chromium 20.00-30.00 Cobalt 15.00-35.00 Nickel 5.00-1000 Zirconium LOO-5.00 Titanium -miMn. 0.15-10.00 Tungsten 2.50-3.00 Iron Balance.

Although tungsten is listed in each list of metals, we regard molybdenum as its full equivalent. Thus, any reference to tungsten in the present specification and claims is meant to include molybdenum and each may be substituted for the other in the percentage range indicated.

As indicated previously, it is preferred that at least 0.5% zirconium be added to a melt immediately prior'to the adding of titanium in order to insure that substantially no reaction between titanium and either oxygen or nitrogen takes place. The use of a smaller proportion of zirconium will in general result in only a partially efiective control of the adverse titanium reactions. There is no critical upper limit to the zirconium proportion to be added piror to the titanium. This will be limited in each instance by the proportion of zirconium desired in the final alloy. Where only a fraction of the final zirconium proportion is added prior to the titanium, the balance may be added as desired.

With specific reference to the forming of the alloy of this invention, all of the metals except zirconium and titanium are melted together in a crucible. At least a portion of the zirconium, and preferably at least 0.5%, is added to the melt and immediately thereafter the titanium is added. The balance of the zirconium, if any, can then be added as desired. In this manner, an alloy containing substantially no oxides and nitrides of titanium is formed and full advantage of the invention may be obtained.

We claim:

1. An alloy comprising essentially the following ingredients in approximately the percentage range indicated:

I 2. An alloy comprising essentially the following ingredients in approximately the percentage range indicated:

Carbon 0.25- 0.50 Manganese 1.00- 2.00 Silicon 1.00- 2.00

4 Chromium 20.00-25.00 Cobalt 14.00-20.00 Nickel 10.00-12.00 Zirconium 1.00- 5.00 Titanium 0. 5- 2.00 Tungsten 2.50- 3.00 Iron Balance.

3. An alloy comprising essentially the following ingredients in approximately the percentage range indicated:

Carbon 0.50- 0.75 Manganese 1.00- 2.00 81110011 1.00- 2.00 Chromium 20.00-30.00 Cobalt 15.00-35.00 Nickel 5.00-10.00 Zirconium 1.00- 5.00 Titanium 0.15-10.00 Tungsten 2.50- 3.00 Iron Balance.

HUGH P. OWENS. EMIL GRADY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,478,420 Payson Aug. 9, 1949 2,491,021 Zimmerman Dec. 13, 1949 2,504,453 Rotherham et a1. Aug. 18, 1950 2,528,867 Day Nov. 7, 1950 

1. AN ALLOY COMPRISING ESSENTIALLY THE FOLLOWING INGREDIENTS IN APPROXIMATELY THE PERCENTAGE RANGE INDICATED: 